We have reported the presence of a sulfhydryl oxidizing enzyme in the male reproductive tract. The enzyme, a sulfhydryl oxidase, catalyzes the reaction 2R-SH plus O2 yields R-S-S-R plus H2O2. The localization of the enzyme within the reproductive tract and its reactivity towards sulfhydryl compounds suggest that the enzyme may play a role in regulating the sulfhydryl chemistry of the tract. Recently, we have purified the enzyme from hamster epididymal fluid to homogeneity on polyacrylamide gels by fractionation procedures involving Sephacryl S-200 gel filtration and ion exchange chromatography on DEAE Bio-Gel A and hydroxylapatite. In the studies proposed in this application renewal, purified enzyme preparations will be characterized with respect to the enzyme's pH and temperature optima, cofactor requirement, substrate specificity, and sensitivity to various inhibitors, and with respect to the effect of ionic strength on the enzyme's activity. In addition to these biochemical investigations, physiological studies will be performed to determine whether the site of synthesis of the enzyme in epididymal fluid is the epididymis itself, or the testis. Experiments will also be performed to determine if the maintenance of enzyme levels within the epididymis is androgen dependent. The proposed studies will increase our understanding of the sulfhydryl chemistry of the reproductive tract and the factors which may control it.